Carburizing material



Patented Dec. 31, 1929 I J UNITED STATES PATENT OFFICE GEORGE W. PRESSELL, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOB TO E. F. l HOUGI-ITON AND COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA CARBURIZING MATERIAL No Drawing. Application filed Iu1y 14, 1928. Serial No. 292,915.

My invention relates to that class of com- The features of the present invention may pound-s,known as carburizers or case-harden be successfully employed with carburizers lng materials, used to increase "the carbon whose carbonaceous material either is initialcontent of the surface of iron and steel obly in the form of grains or in the form of i ,5 jects whereby it is possible to obtain objects dust. The invention is characterized by the with a relatively hard surface. presence of a heav metal oxide in and at the One object of my invention is to provide surface of the car urizing grains or pellets. a novel compound which is a departure from The term heavy metal oxide includes the the usual type of material used in carburizoxides of manganese, iron, chromium, alumiing and case-hardening work. num, nickel, cobalt, lead, copperand-the like, (60

Another object is to provide a relatively and excludes the oxides of the alkali and cheap carburizing material which can be alkaline earth metals. In the choice of the economically manufactured and which at the oxides to be used according to this invention, same time will be of increased.carburizing the oxides with a high oxygen content are activity. preferable. For example, if iron oxide is to A further object is to provide a carburizbe used, the ferric (Fe O or ferrosoferric ing material not only with increased care (Fe og) oxides are preferred; with nickel burizing activity on the initial heat but one and cobalt, the oxides in which the metal is which will be substantially more permanent of the higher valence are more satisfactory.

in its actionand which can be used with suc- The same relation holds fortheoxides of the cess for repeated heats. other metals. I have found that the results Another object is to furnish an improved obtained by the use of manganese dioxi de are process'inthe manufacture of carburizers and especially satisfactory and in the sample of case-hardening materials. Other objects of a suitable carburizer employing this inven- 2 the present invention will be apparent from tion hereinafter discussed, one employing a consideration of the specification and manganese dioxide is given but it is to be claims. understood that other heavy metal oxides At the present time, carburizing commay be used in the manner illustrated.

ounds are manufactured in granular and The efiect of the presenceof the heavy pellet form of various meshes. In general, metal oxide in and at the surface of the carthe carburizers comprise carbonaceous maburizing material is not definitely underterial and energizer. Various methods of stood but due to the increased carburizing manufacturing the grains and pellets are activity both in the initial and in subsequent now in use. For example in the manufacture runs, it is thought that the oxygen is liberated of one type of carburizing material, grains from the oxide under the conditions of carof coke or charcoal or both are treated with burizationy It is well known thatunder certhe energizing material which in turn is ustain conditions, carbon monoxide is evolved ually bound in the pores or on the surface of in the carbu-rizing pot. This is disadvan- 40 the carbonaceous grains by means of an tageous for according to the present theories,

- organic binder. At times, charcoal dust is it 1s carbon dloxlde that gives its carbon to used as a drying agent to prevent the granules the steel. By employing the heavy metal from caking together. Another type of caroxide in and at the surface of the carburizer, burizing material is that made from charcoal the presence of the necessary carbon dioxide or coke dust mixed with the powdered enis assured since it is probable that any carbon ergizer and thereafter formed into pills or monoxide is converted to the dioxide by the pellets by admixing abinding material therepresence of the oxygen of the heavy metal with. If desired, charcoal dust is added to oxide. Oxygen from the air is absorbed by the surface of the grains for the same purthe reduced oxide or metal after the car-- pose as in the manufacture oftheother type burizing heat and therefore the carburizer is of carburizing material. ready for subsequent use.

This theoretical discussion is merely to be considered as a possible explanation of the phenomenon encountered and is not to be considered in any Way limiting the invention involved.

Besides insuring the availability of oxygen during carburization, the heavy metal oxide performs a second important function in those carburizers Whose compounding or manufacture involves the use of binding materials. The heavy metal oxide is highly absorptive and acts most satisfactorily as a drying or dusting agent. The use of this prevents the individual grains of the carburizer from sticking together and settling down into a solid cake during storage or transit. The relatively high density of the oxides precludes the possibility of contamination of the air in the mixing room. This property, as Well as the high Water-absorptive power of the oxides, and the availability of the oxygen during carburization result in a carburizing material of much improved "qualities and carburizing activity.

If the carburizer is one of the type employing an organic binder, it is often desirable to coat the individual grains with an intermediate dusting or drying agent after the addition of the agglutinant and prior to the addition of the heavy metal oxide. In such cases, I have found that infusorial earth is particularly advantageous. The addition of the intermediate drying material, that is to say the infusorial earth or the like, also constitutes part of the present invention. In placg of the infusorial earth, other inert or relatively inert materials such as silica flour or cement may be used or, if desired, a material With carburizing value such as magnesium carbonate, limestone or barium carbonate. The choice of the so-called intermediate drying agent Will depend upon the use for Which the compound is to be employed but for general purposes the infusorial earth is satisfactory. Any substance which is non-hygroscopic and which is capable of drying the grains may be used. Hereinafter, throughout the specification and claims. this material is referred to as an intermediate drying agent.

The use of the intermediate drying agent is optional and the dusting of the grains and the prevention of the caking may be had ontirely by the use of the heavy metal oxide, for example, manganese dioxide. The following process may be employed: A layer of No. 3 mesh charcoal is placed in the hopper of a mixer of suitable construction and then a layer of barium carbonate is superimposed thereon followed by a second layer of charcoal. The addition of the alternate layers of the charcoal and barium carbonate is continued until 258 pounds of No. 3 mesh char coal and 103 pounds of barium carbonate have been added. Following this, 24 pounds of hydrated lime are placed in the hopper. 168 pounds of No. 3 mesh rice coke and a gallon of Water are thoroughly agitated in the revolving mixer and the entire contents of the hopper are dumped therein. The mixing is continued until a uniform distribution of all the materials is obtained. Then 8% gal lons of black strap molasses or other suitable binder are permitted to flow very slowly into the mass. After the addition of this material, the mixing is continued for a suitable length of time until the grains are coated With the molasses. In most cases, a period of four minutes is suflicient after the 8 gallons of black strap molasses have been added. In a specific case, pounds of manganese dioxide are added to the concrete mixer and the mixing continued until the manganese dioxide has had an opportunity to counteract the adhesive nature of the binder and completely coat the individual grains. This requires a relatively short time, and in general practice in four or five minutes the grains Will be completely coated with the heavy metal oxide.

From this process, it Will be seen that the heavy metal oxide forms a coating on the outside of the individual carburizing grains and it is the presence of this manganese dioxide or other heavy metal oxide in and at the surface of the grains which accounts for the satisfactory and unexpected results obtained by the use of the carburizer of this invention. The example given above is merely illustrae tive of one satisfactory carburizer in Which the heavy metal oxide is found in and at the surface of the individual particles, and the carbonaceous material, the energizer, the organic binder and the heavy metal oxide as Well as the amounts thereof may depart Widely from the specific formula of the example.

As hereinbefore pointed out, at times it is desirable to use an intermediate drying material such as infusorial earth, silica or one of the carbonates. If such is advantageous, then the compound, say the infusorial earth, may be added to the mixture following the incorporation of the black strap molasses and prior to the addition of the heavy metal oxide. In the case of infusorial earth, I have found that 15 pounds is a satisfactory amount on the basis of the carbonaceous material, energizer and binder given above, and the use of this 15 pounds of infusorial earth cuts down the amount of managanese dioxide necessary in the above example from 45 pounds to 30 pounds. In the use of illfusorial earth, it is added to the mixer after the agitation With black strap molasses or other binder and the mixing is continued until it dusts or dries the grains and at least partly coats the individual grains. This usually takes about two minutes. The inanganese dioxide is then added and the agitation and mixing continued until the grains are completely covered With the manganese dioxide.

I have found that manganese dioxide is particularly advantageous since it comparatively freely gives up its oxygen during the carburizing operation and thereafter re-absorbs oxygen from the air. Furthermore, it is non-hygroscopic and therefore is an excellent drying agent. It has the further advantage of being of a dark color and of fairly heavy density so that there is very little tendency for the material to contaminate the air in the mixing. The color makes the carburizer very acceptable to the trade.

Obviously also, the product containing the essential ingredients of carburizer as herein outlined may be obtained by other processes and the invention is not to be limited to any particular process of manufacture nor is there any limitation in the proportions of the substances employed in the product since the proportions may be largely varied to suit the particular Work for Which the carburizer is intended.

I claim:

1. Granular carburizing material characterized by the presence of a coating of heavy metal oxide on the surface of the individual carburizing grains.

2. Granular carburizing material characterized by the presence of a coating of manganese dioxide on the surface of the individual carburizing grains.

3. Granular carburizing material comprising carbonaceous material, an energizer in intimate contact therewith and retained in contact by a binding material, and a coating of heavy metal oxide on the surface of the individual carburizing grains.

4. Granular carburizing material comprising carbonaceous material, an energizer in intimate contact therewith and retained in contact by a binding material and coating of manganese dioxide on the surface of the in dividual carburizing grains.

5. Granular carburizing material characterized by the presence of an intermediate drying agent on the surface of the individual carburizing grains and a superposed coating of a heavy metal oxide thereon.

6. Granular carburizing material characterized by the presence of infusorial earth on the surface of the individual carburizing grains and a superposed coating of manganese dioxide.

7. Granular carburizing material comprising carbonaceous material, an energizer in intimate contact therewith and retained in contact by a binding material, infusorial earth thereon and a superposed coating of manganese dioxide on the surface of the individual carburizing grains.

8. Granular carburizing material comprising charcoal and coke grains, barium carbonate and hydrated lime in contact there- GEORGE W. PRESSELL. 

